Page 45 - Let them speak Towards a patient reported outcome measure set for

Outcomes and instruments
of so many instruments. It underlines the need for consensus on outcomes
and instruments, such as the Outcome Measures Working Groups and
expert groups convened by the NIH,38,39 the ERICA PROMs Repository
(Endo-ERN), and the establishment and validation of the National Institutes
of Health Toolbox Cognitive Battery (NIH-TCB) for individuals with ID.28,40,41
Type of reporter
Although instruments are generally developed as one specific type of COA,
similar instruments were completed by different types of reporters (e.g. a
ClinRO instrument used as ObsRO by parents). Furthermore, proxy-reports
were substantially more used (39%) than self-(assisted) reports (23%).
Although the use of proxy-reports is not surprising in populations with ID,
the validity of proxy reflections of unobservable internal states (e.g. anxiety
or depression) is limited, as the personal perspective can only truly be
understood by the individual’s self-report.42 Proxy-raters often assess (HR-)
QoL worse compared to individuals themselves, indicating bias.43–49 PROs
may thus be difficult to measure by proxy-reports,50 although still providing
valuable information.51 It has been suggested that adolescents with ID can
reliably report on their mental health status, with instruments appropriate
to their age, cognitive, and visuospatial functioning.52,53 However, a recent
study illustrated that there is currently no self-report instrument with
acceptable psychometric properties available for assessing (HR-)QoL and
subjective well-being of adolescents with ID.42 Novel methods are upcoming
such as experience sampling methods with the use of apps and ID-friendly
instruments.54,55
2
The emergence of condition-specific and personalized outcome
measurement instruments
In an attempt to measure the impact of a disease and target-specific
phenotypes without the need for multiple tools,56,57 condition-specific (n = 18)
and personalized (n = 6) outcome measurement instruments were used. Also,
tools particularly designed for a specific trial (n = 16) were used. Condition-
specific PROMs have also been developed due to unavailability of proxy-versions
for adults with ID and criticism on appropriateness of the existing instrument’s
content and measurement properties for the target population.56,58 Such
instruments might contain more relevant items to complete, increasing
43